Changing head gasket

Head gasket is the most likely suspect. There are some other tests that could have been done but they most likely wouldn't have identified the source of the leak. Those tests are more for combustion gases in the cooling system and coolant in the tail pipe.

You don't have to have it at top dead center when taking it apart but you will when putting it back together. Do you know what is meant by an "interference" engine?

The cylinder head will probably need to be re-surfaced (due to being warped)
which means that the Machine shop will want to have the head "stripped
down".

Take it apart "as is", but if you rotate it to TDC, you will not have
to worry about the bottom end when you put it back together.

Keep tension on the upper chain when you remove it from the cam gears
so that it does not slip out from the intermediate shaft sprocket.

Thomas

Sorry, forgot to mention that you have an oil cooler... it could be
that the oil cooler is faulty, but the fact that you said it overheated
a few times, probably resulted in the head gasket (or head warp) failure.

You can remove the oil cooler and test it BEFORE you pull the head.

I tested this one with compressed air:

http://www.youtube.com/watch?v=WNYx4Xjr8-I&feature=plcp

Not out of a VR6, but the coolers are pretty much the same.

Thomas

Unless you make something to hold the camshaft in position it is likely going to rotate due to valve spring pressure. It's too much work to try to maintain the relationship while everything is apart. Even if you could, you'd still want to recheck the timing so you're going to be rotating the crankshaft. It's easiest and fastest to just put the crank and cam at TDC, then install the head.

HI ALL YOU MAY FIND CRACKS IN THE HEAD AND HAVE TO REPLACE IT.I WOULD JUST REPLACE THE HEAD WITH A REBUILT 1. GL

The mark on the front crank pulley will not be enough. You need
to check that the camshafts are in the correct position via a
camshaft ruler (some coll it a cam lock tool).

Picture is attached.

Thomas

Yup, but the cam holding tool is for assembling the engine. You were originally asking about taking it apart. If it isn't all the way apart yet you might want to set the crank at top dead center, then take a few pictures of the other pulleys. Use some paint to make the marks more visible if necessary.

A good way to start reassembling is to bring one piston to top dead center, back it up a little so no piston is all the way up, then you can install and torque the head knowing no open valve will hit a piston. Rotate the cam sprocket so it's at top dead center, then back it up too about the same amount. THAT can be easier said than done, especially if you're fighting with two camshafts. The point is no matter where you turn the cams, no valves will be hitting a piston. When everything is close and the timing belt is installed, THEN you can slowly turn the crank forward by hand to top dead center, then check how many teeth you're off on the other sprockets. If you feel a clunk in the crank, stop, back up, and reset the cam sprockets, then slowly try again. When everything appears to be correct, rotate the crank forward two revolutions, stop at TDC, then recheck all the timing marks. During those two revolutions you'll feel the intermittent resistance of a piston coming up on top dead center on the compression stroke, and if you turn it slow enough that pressure will leak out and the crank will start turning easier. That resistance to turning is gradual and soft, and feels a lot different than a valve hitting a piston.

If you loosen the timing belt to move it a few teeth on a sprocket, a camshaft can get away on you due to valve spring pressure pushing on a lobe. If you fight with that more than a few minutes you may want to find that holding tool you mentioned. I watched a former student struggle for hours with a GM engine with four camshafts, and once he borrowed the fixture from the dealer, the job took less than an hour.

Hi all I would pull the #1 spark plug and turn it over. When I felt compression on the hole. I would use a pencil in the hole. Keep turning the crank until the #1 piston is all the way up. Then look at the timing marks. They will be close. Just line the marks and youll be on compression stoke on #1 CYL. Gl

With the valve cover off, turn the engine till the cams can be locked
with a couple of small plates.

The plates don't need to stay in, they are just used to verify #1 TDC.

https://www.2carpros.com/images/external/TimingChain9.jpg

As long as the upper chain does not slip out of the intermediate
gear... and you mark the cam gears to the upper chain, no worries
with loss of timing.

Thomas